"melodic phrase in jazz," 1935 (but said to have been used by musicians since c.1917), of uncertain origin, perhaps a shortened form of riffle, or altered from refrain. The verb is attested from 1942, from the noun. Also in extended use. Related: Riffed; riffing.

riff 1

A solo passage of any sort: He never inflates a movement, never accelerates into showy riffs of excess energy(1917+ Jazz musicians)

A particular variation or version: I have actually eaten something called a pastrami burrito dog, sort of a riff on the oki dog(1990s+)

A piece of personal behavior, esp of entertainment; shtick: allow the star to do character riffs that approximate the sort of things she does as monologues in her one-woman show/ He can make out the riffs and scams of the inner city like a dog picking up a scent(1980s+)